CDTT Virus Files Decrypt & Removal

Written by Brendan Smith

The Cdtt virus is a ransomware-type infection and part of the STOP/DJVU family. This malware family is famous for malicious file ciphering. When the this virus gets into a system, it targets various types of files, like documents, videos, photos, and more. It changes the file structure and appends the “.cdtt” extension to each file, making them unusable without the decryption.

Cdtt Virus Overview

Cdtt

🤔 Cdtt malware belongs to ransomware that belongs to the DJVU/STOP ransomware family. Its main target is to cipher files that are important to you after that ransomware virus asks you to pay the ransom – ($999 – $1999) in Bitcoin.

The Cdtt virus is a malicious program that ciphers your files and coerces you into paying for their restoration. This ransomware ciphers different file types. Encrypted files are identifiable by a distinct “.cdtt” extension. As a result, the affected files become inaccessible and unusable.

Subsequently, the ransomware asks for a ransom payment in Bitcoin from its victims, ranging from $999 to $1999. Typically, a text file with ransom payment guidances is named “_readme.txt”.

Cdtt Ransomware works with Salsa20 encryption algorithms to scramble the contents of the targeted files. Since Cdtt virus employs such a robust encryption method, it becomes quite difficult, if even possible, to find the decryption key without cooperating with the attackers.

Once Cdtt malware finishes the encryption, it shows a ransom note to the user, asking for a ransom payment for the decryption key. The ransom note contains instructions on how to make the payment and often contains threats of data loss or increased ransom amounts if the ransom is not paid within a specified timeframe.

I have compiled an all-encompassing list of potential solutions, advice, and practices to neutralize the Cdtt malware and decrypt and recover your files. In some cases, it may be feasible to restore your files, but sometimes, it may be impossible.

Brendan Smith
Brendan Smith
IT Security Expert
First, perform a PC scan using an antivirus tool!
I will assist you in removing the Cdtt virus and guide you through the process of decrypting or restoring encrypted files. Below, you will find several universally applicable methods to recover encrypted .cdtt files. It is crucial to thoroughly read and comprehend the entire set of instructions. Do not skip any steps. Each step is of utmost importance and must be completed by you.
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📌 Important Note!

It is essential to note that paying off the bill is not a guarantee of the successful recovery of your files. The scoundrels behind the Cdtt virus are not trustworthy. There have been instances where victims have paid the ransom, only to be denied by the cyber criminals with the decryption key provision.

Cdtt uses a unique key for every victim, with one exception:

  • If Cdtt fails to establish a connection with its command and control server (C&C Server) before starting the encryption process, it uses offline keys. An offline key is not unique and is the same for all users, allowing for the decryption of files encrypted by the ransomware.

The Cdtt virus is highly similar to other DJVU ransomware variants like Cdxx, Lkhy, Cdwe and Cdcc. This virus encrypts a wide range of common file types and appends its distinct “.cdtt” extension to all files. For instance, a file named “1.jpg” would be altered to “1.jpg.cdtt” and “2.png” to “2.png.cdtt“.

Upon successful encryption, the virus creates a special text file named “_readme.txt” and places it in every folder containing the encrypted files. It as well adds the readme file to the desktop, so the user will not miss its appearance even without opening folders.

The image below provides a visual representation of files with the “cdtt” extension:

Cdtt Virus - encrypted cdtt files

Encrypted Files by STOP/DJVU Ransomware

NameCdtt Virus
Ransomware family1DJVU/STOP2 ransomware
Extension.cdtt
Ransomware note_readme.txt
RansomFrom $999 to $1999 (in Bitcoins)
Contact[email protected], [email protected]
DetectionBackdoor:Win32/Carrotime.A, Trojan:Win32/RiseProStealer.A!MTB, Troj/Krypt-ADH
Symptoms
  • Installs password-stealing Trojan on the system, like Vidar Stealer or RedLine Stealer;
  • Adds a list of domains to the HOSTS file to block access to certain security-related sites;
  • Encrypts most of your files (photos, videos, documents) and adds a particular “.cdtt” extension;
  • Manages to install a SmokeLoader backdoor;
  • Can delete Volume Shadow copies to make victim’s attempts to restore data impossible;
Fix Tool To remove possible malware infections, scan your PC:


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This message asking for payment is for restoring files via decryption key:

_readme.txt Ransom Note

The “_readme.txt” file (STOP/DJVU Ransomware).

Cdtt ransomware arrives as a set of operations that are used to carry out different activities on a victim’s computer. One of the first ones being launched is winupdate.exe, a tricky process that displays a fraudulent Windows update alert during the attack. This is meant to convince the victim that their PC has become slow because of a Windows update.

At the same time, the ransomware runs another process (whose name commonly consists of 4 random characters) which starts scanning the system for target files and ciphering them. Then the ransomware deletes Volume Shadow Copies from the system disk through the following CMD command:

vssadmin.exe Delete Shadows /All /Quiet

Once erased, it becomes virtually impossible to recover the previous computer state using System Restore Points. The problem is, that ransomware operators are eliminating any built-in Windows techniques that could help the victim to restore files for free. In addition, the crooks modify the Windows HOSTS file by appending a list of domains to it and directing them to the localhost IP. As a result, the victim will see a DNS_PROBE_FINISHED_NXDOMAIN error when accessing one of the blocked websites.

We’ve observed that ransomware attempts to block websites that post various how-to guides for computer users. It is obvious that by hindering specific domains, the crooks are seeking to stop the victim from accessing relevant and helpful ransomware-attack-related information online. The virus also stores two .txt files on the victim’s computer that present information related to the attack – the public key of this victim and personal ID. These two files are named bowsakkdestx.txt and PersonalID.txt.

Cdtt ransomware virus saves public encryption key and victim's id in bowsakkdestx.txt file

After all these modifications, the malware doesn’t halt. Variants of STOP/DJVU are inclined to release Vidar password-stealing Trojan on compromised systems. This threat possesses a large list of capabilities, including:

  • Gathering sensitive data by running malicious software on the victim’s computer.
  • Acquiring unauthorized login credentials of Steam, Telegram, and Skype accounts.
  • Manipulating and viewing files on the victim’s computer without their knowledge.
  • Stealing cryptocurrency wallets from the victim’s system.
  • Granting the hackers remote control over the victim’s computer for various malicious activities.
  • Extracting sensitive information such as browser cookies, saved passwords, and browsing history.

The cryptography algorithm used by the DJVU/STOP virus is AES-256. So, if your data got encrypted with an online decryption key, the possibility of getting your files back is quite low. The thing is, this key is unique for each victim, and picking it will take too much time.

Retrieving the online decryption key in any other way is also nearly impossible. It is kept on a command server controlled by the criminals who spread the Cdtt infection. For receiving decrypting code the payment should be $1999. To get the payment details, the victims should contact the fraudsters by email ([email protected]).

The message by the ransomware states the following information:

ATTENTION!

Don't worry, you can return all your files!
All your files like pictures, databases, documents, and other important are encrypted with the strongest encryption and unique key.
The only method of recovering files is to purchase a decrypt tool and a unique key for you.
This software will decrypt all your encrypted files.
What guarantees do you have?
You can send one of your encrypted files from your PC and we decrypt it for free.
But we can decrypt only 1 file for free. The file must not contain valuable information.
You can get and look video overview decrypt tool:
https://we.tl/t-FCWSCsjEWS
The price of private key and decrypt software is $1999.
A discount of 50% is available if you contact us first 72 hours, that's the price for you is $999.
Please note that you'll never restore your data without payment.
Check your e-mail "Spam" or "Junk" folder if you don't get an answer for more than 6 hours.


To get this software you need to write on our e-mail:
[email protected]

Reserve an e-mail address to contact us:
[email protected]

Your personal ID:
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

How To Remove STOP/Djvu Ransomware?

Remove Cdtt Virus with Gridinsoft Anti-Malware

We have also been using this software on our systems ever since, and it has always been successful in detecting viruses. It has blocked the most common Ransomware as shown from our tests with the software, and we assure you that it can remove Cdtt Virus as well as other malware hiding on your computer.

Gridinsoft Anti-Malware - Main Screen

To use Gridinsoft for remove malicious threats, follow the steps below:

1. Begin by downloading Gridinsoft Anti-Malware, accessible via the blue button below or directly from the official website gridinsoft.com.

2.Once the Gridinsoft setup file (setup-gridinsoft-fix.exe) is downloaded, execute it by clicking on the file.

setup-gridinsoft-fix.exe

3.Follow the installation setup wizard's instructions diligently.

Gridinsoft Setup Wizard

4. Access the "Scan Tab" on the application's start screen and launch a comprehensive "Full Scan" to examine your entire computer. This inclusive scan encompasses the memory, startup items, the registry, services, drivers, and all files, ensuring that it detects malware hidden in all possible locations.

Scan for Cdtt Virus Ransomware

Be patient, as the scan duration depends on the number of files and your computer's hardware capabilities. Use this time to relax or attend to other tasks.

5. Upon completion, Anti-Malware will present a detailed report containing all the detected malicious items and threats on your PC.

The Cdtt Virus was Found

6. Select all the identified items from the report and confidently click the "Clean Now" button. This action will safely remove the malicious files from your computer, transferring them to the secure quarantine zone of the anti-malware program to prevent any further harmful actions.

The Cdtt Virus has been removed

8. If prompted, restart your computer to finalize the full system scan procedure. This step is crucial to ensure thorough removal of any remaining threats. After the restart, Gridinsoft Anti-Malware will open and display a message confirming the completion of the scan.

Remember Gridinsoft offers a 6-day free trial. This means you can take advantage of the trial period at no cost to experience the full benefits of the software and prevent any future malware infections on your system. Embrace this opportunity to fortify your computer's security without any financial commitment.

Trojan Killer for “Cdtt Virus” removal on locked PC

In situations where it becomes impossible to download antivirus applications directly onto the infected computer due to malware blocking access to websites, an alternative solution is to utilize the Trojan Killer application.

Trojan Killer - Main View

There is a really little number of security tools that are able to be set up on the USB drives, and antiviruses that can do so in most cases require to obtain quite an expensive license. For this instance, I can recommend you to use another solution of GridinSoft - Trojan Killer Portable. It has a 14-days cost-free trial mode that offers the entire features of the paid version. This term will definitely be 100% enough to wipe malware out.

Trojan Killer is a valuable tool in your cybersecurity arsenal, helping you to effectively remove malware from infected computers. Now, we will walk you through the process of using Trojan Killer from a USB flash drive to scan and remove malware on an infected PC. Remember, always obtain permission to scan and remove malware from a computer that you do not own.

Step 1: Download & Install Trojan Killer on a Clean Computer:

1. Go to the official GridinSoft website (gridinsoft.com) and download Trojan Killer to a computer that is not infected.

Download Trojan Killer

2. Insert a USB flash drive into this computer.

3. Install Trojan Killer to the "removable drive" following the on-screen instructions.

Install Trojan Killer to Removable Drive

4. Once the installation is complete, launch Trojan Killer.

Step 2: Update Signature Databases:

5. After launching Trojan Killer, ensure that your computer is connected to the Internet.

6. Click "Update" icon to download the latest signature databases, which will ensure the tool can detect the most recent threats.

Click Update Button

Step 3: Scan the Infected PC:

7. Safely eject the USB flash drive from the clean computer.

8. Boot the infected computer to the Safe Mode.

9. Insert the USB flash drive.

10. Run tk.exe

11. Once the program is open, click on "Full Scan" to begin the malware scanning process.

Searching Cdtt Virus Virus

Step 4: Remove Found Threats:

12. After the scan is complete, Trojan Killer will display a list of detected threats.

Searching Cdtt Virus Finished

13. Click on "Cure PC!" to remove the identified malware from the infected PC.

14. Follow any additional on-screen prompts to complete the removal process.

Restart needed

Step 5: Restart Your Computer:

15. Once the threats are removed, click on "Restart PC" to reboot your computer.

16. Remove the USB flash drive from the infected computer.

Congratulations on effectively removing Cdtt Virus and the concealed threats from your computer! You can now have peace of mind, knowing that they won't resurface again. Thanks to Gridinsoft's capabilities and commitment to cybersecurity, your system is now protected.

Video Guide


How To Decrypt .cdtt Files?

How to restore big files?

Try deleting .cdtt extension on a few big files and opening them. This malware has issues with large file encryption. Either the virus read and did not lock the file, or it bugged and did not add the filemarker. If your files are very large (2GB+), such a situation is highly probable. Please, text me in the comments whether this helped you or not.

The newest extensions were released around the end of August 2019 after the criminals made changes. As a result of the changes made by the criminals, STOPDecrypter is no longer backed. It has been replaced with the Emsisoft Decryptor for STOP Djvu Ransomware developed by Emsisoft.

You can download free decryption tool here: Decryptor for STOP Djvu.

  1. Download and run the decryption tool.

    Start downloading the decryption tool.

    Make sure to launch the decryption utility as an administrator. You need to agree with the license terms that will come up. For this purpose, click on the “Yes” button:

    Emsisoft Decryptor - license terms

    As soon as you accept the license terms, the main decryptor user interface comes up:

    Emsisoft Decryptor - user interface

  2. Select folders for decryption.

    Based on the default configurations, the decryptor will by default choose the accessible directories to decode the currently reachable drives (the connected ones), including the network drives. Extra (optional) locations can be selected with the assistance of the “Add” button.

    Decryptors typically propose several options depending on the specific malware family. The present possible options are shown in the Options tab and can be turned on or turned off there. You may discover a detailed list of the currently active Options below.

  3. Click on the “Decrypt” button.

    As soon as you add all the desired locations for decryption to the list, click on the “Decrypt” button to initiate the decryption procedure.

    Note that the main screen may turn you to a status view, letting you know of the active process and the decryption statistics of your data:

    Emsisoft Decryptor - the decryption statistics

    The decryptor will notify you as soon as the decryption procedure is completed. If you need the report for your papers, you can save it by choosing the “Save log” button. Note that it is also possible to copy it directly to your clipboard and paste it into emails or messages here if you need to do so.

The Emsisoft Decryptor might display different messages after a failed attempt to restore your files:

✓ Error: Unable to decrypt a file with ID: [your ID]

Emsisoft failed to find a corresponding decryption key in their database.

✓ No key for New Variant online ID: [your ID]

Notice: this ID appears to be an online ID, decryption is impossible

Malware uses an online key to cipher your files. There is no one to share the decryption key with you. File recovery is only possible through paying the ransom. 🙁

✓ Result: No key for new variant offline ID: [example ID]

This ID appears to be an offline ID. Decryption may be possible in the future.

An offline key was used, but files could not be restored (the offline decryption key isn’t available yet). But, receiving this message is good news for you, since it is possible to restore your files in the future. 🙂

It can take a few weeks or months until the decryption key gets found and uploaded to the decryptor. Please follow updates regarding the decryptable DJVU versions here.

✓ Remote name could not be resolved

This stands for a DNS issue. Consider resetting your HOSTS file to default.

How to Restore .cdtt Files?

In some cases ransomware is not doom for your files…

The Cdtt ransomware encryption algorithm is next: it encrypts every file byte-by-byte, then saves a duplicate, erasing (not overriding!) the initial file. Thus, the information on the file placement on the disk drive is lost, but the original file is not removed from the disk. The cell, or the sector where this file was kept, can still hold this file, but it is not listed by the file system and can be rewritten by data that has been loaded to this drive after the removal. Hence, it is possible to recover your files using special software.

I recently had my PC infected by this virus. It managed to bypass 2 Antivirus software and 2 malware fighters.

Anyway, after realizing it was an online algorithm, it was impossible to retrieve my encrypted files. I also had my backup drive plugged in at the time of the virus, and this was also infected, or so I thought. Every folder within my backup drive had been infected and was encrypted. However, despite losing some important files, I retrieved almost 80% of my 2TB storage.

When I started going through the folders, I noticed the readme.txt ransom note in every folder. I opened some of the folders and found that all files that were not in a subfolder within that folder had been encrypted. However, I found a flaw and a glimmer of hope when I went into the subfolders in other folders and found that these files had not been encrypted. Every folder within my c and d drives, including subfolders, had been encrypted, but this was not the case with the backup drive. Having subfolders created within a folder has saved 80% of my data.

As I said, I believe this to be only a small loophole on a backup drive. I’ve since found a further 10 % of my data on another hard drive on a different PC. So my advice is if you use a backup drive, create subfolders. I was lucky, I guess. But I was also unlucky that the virus hit as I was transferring some files from my backup.

Hopefully, this can help some other people in my situation.

Jamie Newland
Some pointers for recovery repair of Cdtt files (true for all STOP/DJVU variants):

  • I have seen Stop/Djvu variants fail to encrypt deeper nested folders, so you can check that. You may find those are not encrypted.
  • This ransomware saves encrypted data to a new file and deletes the original. So there’s a slight chance part of that deleted file can be recovered using file recovery software. It’s unlikely the folder structure can be restored, so a free tool like PhotoRec may be as good as any.
  • This ransomware only partially encrypts (about the first 150 KB), so depending on file size and type of data, the non-encrypted part may be recoverable.
  • Joep

    Recovering your files with PhotoRec

    PhotoRec is an open-source program, which is created for data recovery from damaged disks, or files recovery in case they are unintentionally deleted. However, as time has gone by, this program can restore files in 400 different formats. Hence, it can be used for file recovery after the Cdtt attack.

    First, you need to download this app. It is 100% free, but the developer notifies that there is no assurance that the files will be restored. PhotoRec is spread together with another utility of the same developer – TestDisk. The program archive will have a TestDisk name but don’t worry. PhotoRec files are right inside.

    To run PhotoRec, you need to find and open “qphotorec_win.exe” file. No installation process is needed – this program has all the files it needs inside of the archive, hence, you can fit it on your USB drive, and help your friends/parents/anyone who has been attacked by Cdtt ransomware.

    PhotoRec file in the folder for restore Cdtt files

    After the start, you will witness the screen showing you the entire list of your drives. However, this information is presumably useless, because the required menu is placed a bit higher. Click this bar, then choose the disk which was attacked by ransomware.

    Choose the disc in PhotoRec

    After choosing the disk, you need to opt for the destination folder for the retrieved files. This menu is located at the lower part of the PhotoRec window. The best choice is to export them on a USB drive or any other type of removable disk.

    Choosing the destination folder of recovery Cdtt files

    Then, you need to indicate the file formats. This setting is located at the bottom, too. As it was mentioned, PhotoRec can recover files of about 400 different formats.

    Choose the file format

    Finally, you can initiate file retrieval by pressing the “Search” button. You will view the screen where the outcomes of the scan and recovery are shown.

    Recovery process

    Cdtt files recovery Video Guide.


    Frequently Asked Questions

    🤔 How can I open “.cdtt” files?

    No way. These files are encrypted by ransomware. The contents of encrypted files are not available until they are decrypted.

    🤔 This virus has blocked the infected PC: I can’t get the activation code.

    In this situation, you need to prepare the memory stick with a pre-installed Trojan Killer.

    🤔 Decryptor did not decrypt all my files, or not all of them were decrypted. What should I do?

    Have patience. You are infected with the new version of STOP/DJVU ransomware, and decryption keys have not yet been released. Follow the news on our website.

    We will keep you posted when new keys or new decryption programs appear.

    🤔 What can I do right now?

    The Cdtt ransomware encrypts only the first 150KB of files. So MP3 files are rather large, some media players (Winamp for example) may be able to play the files, but – the first 3-5 seconds (the encrypted portion) will be missing.

    You can try to find a copy of an original file that was encrypted:

    • Files you downloaded from the Internet that were encrypted and you can download again to get the original.
    • Pictures that you shared with family and friends that they can just send back to you.
    • Photos that you uploaded on social media or cloud services like Carbonite, OneDrive, iDrive, Google Drive, etc
    • Attachments in emails you sent or received and saved.
    • Files on an older computer, flash drive, external drive, camera memory card, or iPhone where you transferred data to the infected computer.

    If the guide doesn’t help you to remove the infection, please download the GridinSoft Anti-Malware that I recommended. Do not forget to share your experience in solving the problem. Please leave a comment here! This can help other victims to understand they are not alone. And together we will find ways to deal with this issue.

    I need your help to share this article.

    It is your turn to help other people. I have written this guide to help people like you. You can use the buttons below to share this on your favorite social media Facebook, Twitter, or Reddit.

    Brendan Smith
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    References

    1. My files are encrypted by ransomware, what should I do now?
    2. About DJVU (STOP) Ransomware.
    How to Decrypt .CDTT File and Remove CDTT Virus?
    Article
    How to Decrypt .CDTT File and Remove CDTT Virus?
    Description
    I'm here to help you get rid of the Cdtt virus and walk you through the steps to decrypt or restore your encrypted files. Check out the methods below; they can be applied universally to recover .cdtt files. Make sure to read and understand all the instructions carefully—don't skip any steps. Each one is crucial and requires your attention to complete successfully.
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    About the author

    Brendan Smith

    I'm Brendan Smith, a passionate journalist, researcher, and web content developer. With a keen interest in computer technology and security, I specialize in delivering high-quality content that educates and empowers readers in navigating the digital landscape.

    With a focus on computer technology and security, I am committed to sharing my knowledge and insights to help individuals and organizations protect themselves in the digital age. My expertise in cybersecurity principles, data privacy, and best practices allows me to provide practical tips and advice that readers can implement to enhance their online security.

    2 Comments

    1. Virgilio Tigo January 24, 2024

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